How compile a java file to .class who use others .class. (if it's possible)

I get lib webrtc in a .aar, and I need to modify one file of this lib. We can call this file tomtom.class for this example

So I unzip this .aar to get many .jar and in those .jar there the file tomtom.class who need to be replaced. I have the new version of file tomtom in java because I edit it. But now I need to compile it for replacing the old tomtom.class. Of course, this file uses other classes inside this lib webrtc.

So is it possible to compile a java file who use other compiled file?

After many tried of use classpath. Or other method I find on Internet. None work, maybe it's me who is a moron but whatever..

How I replaced my file on a lib already compiled (it's the webrtc lib).

I put a copy of the file decompiled in my project on android studio. I can modify it like I want. And this decompiled file can compile with the lib I had in the folder lib. I build the project and I go to the temp file to get the compiled file. Then I can replace the one in .aar by the file compiled I just modify.